At that point it's appealing to the least sophisticated investors, which to me is the first signal of a bubble.
The nature of a ponzi scheme is that it starts small, but then has to appeal to an ever larger group. This ends with mass advertising to reach the biggest group of all. Then what?
Couple this with the tone. Crypto is being marketed as an investment, not as a utility, not as a currency. Its sole appeal is "it will go up".
Crypto itself is mostly a solution looking for a (legal) problem. While the killer app is facilitating illegal activity (which has some value for moral, but illegal activity - alas a minority of the actual use case) that's a hard sell. Finding a legal killer app though is proving elusive. Most things it _can_ do are already done better/faster/cheaper/simpler another way.
Of course it has some utility, but nowhere near the hype levels.
Tech stocks - yes, they are high, and will likely correct some. But apple, Google, Microsoft, amazon, Facebook and friends are all generating huge amounts of revenue and profit. Their stock values are massive, but their profit levels are unprecedented.
Startups get a lot if attention, but from VCs which is not public money, and not traded to the public, so is a different kind of bubble, unrelated to the 1929 depression etc.
Or for some reason think there is going to be a single event that will finally end cryptocurrencies. Or they have an agenda and want them to end.
It's not a single bubble, that stuff happened several times already. They lost more than 50% of their value in a short amount of time, several times already.
It's a boiler. Its periodic bubbles, over and over again. Price fluctuations, slow climbing, then fast climbing, then it goes down, repeats. It has happened already, and it will be happening again and again.
Every time you will be watching, thinking: this time, this is 'the big bubble' and it will burst and cryptocurrencies will be no more. Except they will continue boiling, prices will go up and down, and you will have to wait for the next time.
There's also the probability of a 'flippening' event in the future, because ETH is no longer PoW. So ETH would switch to be the #1 currency. Or maybe not.
But the cat is out of the bag, and cryptocurrencies are here to stay, and I would even say in any four year period they will still gain more than any other kind of asset for the foreseeable future.
The current level seems to be pitched at "everyone". After that there's not much place to go. There are some territories currently excluded and they may come into the fold, but probably won't.
The root problem is that it's utility is limited, and as yet has not found a way to grow that utility in proportion to its overall growth.
By contrast a stock like say apple seems (and may be) bonkers, but apple has shown consistent utility growth. They improve sales by appealing to more market. People by an iPhone to use it, not to keep it and sell it for more.
Of course crypto may not crash. Red flags don't mean certain collapse. They are, after all, just red flags.
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